Assessing the impacts of geological factors on the thermo-economic performance of ground coupled heat pump systems

Zhao, Zilong

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https://hdl.handle.net/2142/120207 Copy

Description

Title

Assessing the impacts of geological factors on the thermo-economic performance of ground coupled heat pump systems

Author(s)

Zhao, Zilong

Issue Date

2023-03-22

Director of Research (if dissertation) or Advisor (if thesis)

Wang, Xinlei

Doctoral Committee Chair(s)

Wang, Xinlei

Committee Member(s)

• Lin, Yu-Feng
• Stumpf, Andrew John
• Wang, Pingfeng
• Wang, Xiaofei

Department of Study

Engineering Administration

Discipline

Agricultural & Biological Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Ground source heat pump
• Geothermal energy
• Green building
• Modeling and simulation

Abstract

Despite the intensive studies that have been made, the penetration of geothermal heat exchangers (GHEs) and ground coupled heat pump (GCHP) systems has been constrained due to high initial cost and land occupation. As indicated by the documented research, the accumulative costs of GCHP vary case-by-case and its optimal design highly correlates with the thermophysical properties of the local geology and groundwater system. Therefore, this research examined the impacts of geologic factors on the performance of GCHPs, regarding the thermal responsive behavior in the ground and the potential economic benefits that may be imposed on the heat pump operation. A thorough literature review on the studies of integrating the presence of groundwater in the GHE model was first conducted. The challenges in system integration, strategies through industry standard models, and commonly used models that have been proved effective were identified and presented. Based on one of the approaches provided in the literature review, a 3-dimensional numerical model was applied to conduct a case study under complex subsurface conditions at the University of Illinois at Urbana-Champaign campus. Though the groundwater flow was previously found to be limited, the hydrogeological conditions were included in the model such as heterogeneous moisture content and flowing seepage, to quantify its impacts on the coefficient of performance (COP) of heat pump. The GCHP-coupled building, as LEED-Platinum-Certified, has significantly lowered heating-cooling loads compared with traditional building energy systems. This GHE model also returned additional benefits by informing system management to alleviate potential overcooling and overheating of the ground. As the last part of the research, a reliability-based design optimization was applied on an analytical GHE model to address how the uncertainties of geological factors affect the optimal design parameters and total costs of the GCHP. The results of this research may help close the energy efficiency gap and facilitate the implementations of GCHP systems within subsurface environments with a complex geology.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Zilong Zhao

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